Extension step ladder



July 15, 1958 R. c. MCKINNIE EXTENSION STEP LADDER Filed Dec. 20, 1956 v INVENTOR. floxmu'CMcKmmg W6 ad FIG.5.

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United States Patent EXTENSION STEP LADDER Roxton C. McKinnie, Los Angeles, Calif. Application December 20, 1956, Serial No. 629,600

2 Claims. (Cl. 228-17) This invention relates general-1y to ladders and more particularly to an improved combination step and extension ladder.

Conventional step ladders usually comprise a pair of front and rear legs pivoted together at their upper ends to open and close in scissors fashion. Generally, a pail shelf and spreader members are provided intermediate theends of the front and rear legs. The primary function of the rear legs is simply that of a support means for the upper portion of the front legs and to this end the rear legs generally comprise a pair of elongated side members suitably braced by a lattice network.

A primary object of the present invention is to provide an improved step ladder in which the rear legs serve the dual function of supporting the front legs to provide a step ladder when in one position and to provide an extension ladder with the front legs when in a second positlOIl:

Another important object of the present invention is to provide a combination step and extension ladder of the above type which does not employ appreciably more material or parts than are used in present day conventional step ladders alone.

Still another object is to provide a step ladder which may be positively locked in a first position as a step ladder and in a second position as an extension ladder whereby the entire structure is completely safe and reliable and may be easily converted manually from one position to the other.

Still another object is to provide a combination step and extension ladder adapted to co-ope-rate with an auxiliary set of elongated rear legs to enable conversion of the extension ladder into a second step ladder of increased height.

Briefly, these and many other objects and advantages of the present invention are attained by providing a conventional type step ladder structure having front legs and rear legs pivoted together adjacent their upper ends. In accordance with the invention, the rear legs are actually in the form of an upside down ladder corresponding to the front legs and provided with a series of steps. The rear legs are shorter than the front legs by a given distance and are arranged to be pivoted at a distance from the top of the front legs corresponding to this given distance such that when the front and rear legs are spread apart in the form of a conventional step ladder, the portions of the legs resting on the floor are level.

Suitable links are provided such that the rear legs may be swung from their upside down position about the pivot points to an upright position such that they bear against the upper portion of the front legs over the above referred Locking means are provided at the upper ends of the front legs to secure the rear legs in this upright position whereby an extension ladder is provided. An auxiliary set of rear legs may be used with the extension ladder structure to provide a second step ladder considerably larger than the first one.

A better understanding of this invention will be had by referring to a preferred embodiment thereof as illustrated in the accompanying drawings, in which:

Figure 1 is an elevational cross section of the ladder in the position of a step ladder;

Figure 2 illustrates the ladder of Figure 1 after conversion to an extension ladder;

Figure 3 is an enlarged perspective view of that portion of the ladder enclosed in the circular arrow 3 of Figure 1;

Figure 4 is an enlarged front view of the step ladder structure taken in the direction of the arrow 4 of Figure 1;

Figure 5 illustrates the ladder in extension ladder form co operating with an auxiliary set of rear legs to provide a larger step ladder; and,

Figure 6 is a detailed View of that portion enclosed within the circular arrow 6 of the step ladder shown in Figure 5.

Referring to Figure 1, the improved ladder of this invention is shown as comprising a pair of front legs 10 and a pair of rear legs 11 provided respectively with steps such as at 12 and 13. The rear legs 11 and steps 13 are actually of the same structure as the front legs 10 and steps 12 but are in an upside down position and have an overall length somewhat shorter than the front legs.

As shown in Figure l, the rear legs 11 are secured to the front legs 10 by suitable pivot means in the form of a bracket 14 and pivot 15, positioned downwardly from the top ends of the front legs 10 a given distance substantially equal to the difference in the lengths between the front and rear legs. The arrangement is such that the rear legs 11 may be folded against the front legs 10 for storage or spread in scissors fashion to provide a conventional type step ladder as illustrated in Figure l. A further reinforcing member 16 extending from the top step of the front legs 10 to the pivot points 15 is provided to insure suflicient rigidity of the pivot support structure.

In the embodiment illustrated in Figure 1, the step ladder is provided with a pail shelf 17 secured to the front legs 10 by a suitable link mechanism 18 pivoted between the rear portion of the pail shelf and the front legs 10. Also provided are shelf support means comprising braces 19 pivoted to the rear legs 11 and secured to the sides of the shelf at its forward portion.

Figure 2 illustrates the front and rear legs in a second position to form an extension ladder. Thus, by swinging the rear legs 11 about the pivot point 15 into an upright position as illustrated in Figure 2, it will be noted that the rear legs have an overlapping portion bearing against the front legs and equal to the referred to given distance.

The manner in which the rear legs are secured in their first position as a step ladder as shown in Figure 1, and in their second position as an extension ladder as shown in Figure 2, will be clear by referring to the enlarged perspective views of Figures 3 and 4 illustrating the shelf support means in detail. As shown in Figure 3, the lower end of the brace member 19 is bent as at 20 to provide a horizontal portion having a small opening 2.1, and a vertical depending portion having a second opening 22. The opening 22 is arranged to receive a bolt to pivotally mount the lower end of the brace 19 to the side of the pail shelf. The opening 21 in the horizontal portion of the brace 19 is adapted to receive a locking pin 23 secured to the rear legs 11 as by a suitable chain 24. This locking pin 23 is adapted to pass through the opening 21 and be received in an eye bracket 25 rigidly secured to the rear legs 11. The arrangement is such that when the rear legs are in the step ladder position as shown in Figure 1, the opening 21 and eye of the bracket 25 register and the pin 23 may be passed through both openings to securely lock the pail shelf 17 to the rear legs 11. The pail shelf thus serves to secure the front and rear legs in proper position such that the apparatus may be employed as a step ladder.

When converting the step ladder to an extension ladder, the pin 23 is manually removed from the opening 21 and eye 25 and the rear legs 11 then simply swung about the pivot point 15 to an upright position such as shown in Figure 2. In this position, it will be noted that the 'eye bracket 25 is now adjacent the upper end of the front legs 10 in position to receive a simple hook 26 secured to the upper ends of the front legs whereby the hook 26 co-operating with the bracket 25 and the pivot bracket 14 serve to securely hold the rear legs in the upright extension ladder position. It Will be evident, therefore, that the lock receiving means in the form of the eye bracket 25 serves a dual function in that, in the step ladder position it receives the locking pin 23, while in the extension ladder position it receives the hook 26.

From Figure 4 it will be noted that a similar brace member 19 and bracket structure 25 is provided on the inside of the other rear leg.

Referring now to Figure -5, there is illustrated an auxiliary set of rear legs 27 adapted to co-operate with the extension ladder formed by the front legs 10 and the rear legs 11. The auxiliary rear legs 27 comprise a conventional lattice network and serve simply as a support for the extension ladder. The manner in which the upper ends of the auxiliary legs are secured to the upper end of the extension ladder is illustrated clearly in Figure 6 wherein it will be noted that a looped bracket 28 is rigidly secured to the upper end of the auxiliary rear legs 27 and adapted to encircle the upper ends of the extension ladder legs. When the rear legs 27 are swung or retated to the spread position, the looped bracket 28 swings downwardly to be received Within a suitable notch 29 provided at the upper ends of the legs of the extension ladder whereby the auxiliary rear legs form an adequate support for the extension ladder and an oversized step ladder is provided.

4 I l The invention, therefore, is not to be thought of as limited to the specific details set forth for illustrative purposes.

What is claimed is:

1. In a combination step and extension ladder including a pair of front legs and a pair of rear legs having a plurality of steps respectively supported therebetween and in which said rear legs are shorter than said front legs by a given length and pivoted in an upside down position to said front legs at points spaced substantially said given length from the top of said front legs when in a first position to provide a step ladder, and including a pail shelf having a rear portion secured to said front legs for swinging movement to an out of the way position, the improvement comprising: lock receiving means secured to said rear legs immediately below said pail shelf; at least one brace member having one end pivotally secured a to one of said rear legs at a point above said shelf and From the above description, it will be evident that the present invention provides a simply operated combination step and extension ladder employing a minimum number of parts and in which positive locking means are provided. Minor modifications within the scope and spirit of this invention will occur to those skilled in the art.

having its other end pivoted to the forward portion of said pail shelf; temporary fastening means on the said other end of said brace for securing said other end of said brace to said lock receiving means whereby said pail shelf serves to support said front and rear legs in the form of a step ladder when in said first position; and means on the upper end of at least one of said front legs for holding the upper portion of at least one of said rear legs when said rear legs are pivoted about said points to an upright position to form an extension ladder, said brace automatically and simultaneously moving said pail shelf to said out of the Way position upon said pivoting of said rear legs to said upright position.

I 2. The combination of claim 1, in which said fastenlng means comprises elongated pins adapted to be positioned in registered openings passing through said brace members and lock receiving means when said ladder is in the position of a step ladder.

References Cited in the file of this patent UNITED STATES PATENTS 476,179 Whitehurst May 3 1, 1892 603,848 Herder May 10, 1898 1,351,146 Zerlini Aug. 3 1,. 1920 1,671,801 White May 29, 1928 

